Immunogenicity of one and two doses of Gardasil®9 in Tanzanian girls in the DoRIS Trial

Tanzanian girls received one to three doses of Gardasil®9 in the DoRIS randomised trial. Blood samples from one and two-dose Gardasil®9 recipients were collected at months (M)0, M7, M12, M24, and M36 for testing via an HPV Multiplex immunoassay. All participants were HPV 16, HPV 31, and HPV 58 seropositive at M36. For the one-dose group, 96.8-98.2% of girls were seropositive for HPV 11, HPV 18, and HPV 33 and 73.0-87.7% seropositive for HPV 6, HPV 45 and HPV 52. For the two-dose group, all participants were HPV 6, HPV 11, HPV 18, and HPV 33 seropositive, while 98.6% seropositive for HPV 45 and HPV 52. Geometric mean concentrations (GMCs) were higher in the two-dose group compared to the one-dose group but all GMCs in the one-dose group had plateaued by M24 and remained stable to M36. HPV vaccine immune responses in this study will continue through nine years post-vaccination. ClinicalTrials.gov ID: NCT02834637; Registration Date: 2016-06-29; https://www.clinicaltrials.gov/study/NCT02834637 .